Cytokines are small to medium sized proteins and glycoproteins that mediate highly potent biological effects on many cell types in networks or cascades. They have critical roles in hematopoiesis, inflammatory responses and the development and maintenance of immune responses. Typical properties in networks of cytokines are pleiotropy, redundancy, synergistic activity and antagonistic effects upon each other (Townsend and McKenzie, J. Cell Sci., 2000, 113, 3549-3550). Knowledge of how cytokine networks are comprised and operate is important in understanding how they mediate their diverse effects on biological systems (Townsend and McKenzie, J. Cell Sci., 2000, 113, 3549-3550).
Interferon-gamma (IFN-gamma) is a cytokine secreted by activated T lymphocytes and natural killer (NK) cells. It is involved in the modulation of a wide variety of immunological and inflammatory responses including activation of macrophages, cytotoxic T cells and Natural Killer (NK) cells, regulation of antibody production by B lymphocytes and control of apoptosis (Billiau, Adv. Immunol., 1996, 62, 61-130).
Interferon gamma receptor complexes are expressed on almost all nucleated cells and show species specificity in their ability to bind IFN-gamma (Dorman and Holland, Cytokine Growth Factor Rev., 2000, 11, 321-333). The functional interferon gamma receptor is composed of two 90 kDa polypeptides designated interferon gamma receptor 1 (also known as IFNGR1, IFN-gamma receptor-alpha chain and CD119w) and interferon gamma receptor 2 (also known as IFNGR2, IFN-gamma receptor-beta, IFN-gamma transducer 1, AF-1 and GAF).
The extracellular portion of interferon gamma receptor 1 contains the IFN-gamma ligand-binding domain and the intracellular portion contains the domains necessary for signal transduction and receptor recycling (Dorman and Holland, Cytokine Growth Factor Rev., 2000, 11, 321-333). In the absence of stimulation, interferon gamma receptors 1 and 2 are not strongly associated with each other. Upon binding of IFN-gamma as a homodimer to the two interferon gamma receptor 1 proteins, interferon gamma receptors 1 and 2 and their constitutively-associated Janus kinases (JAK1 and JAK2, respectively) are brought into proximity so that the signaling cascade can begin via phosphorylation of tyrosine-440 on interferon gamma receptor 1 (Dorman and Holland, Cytokine Growth Factor Rev., 2000, 11, 321-333). Signals are transmitted to the nucleus via the Jak-STAT mechanism of signal transduction involving a cascade of tyrosine phopshorylations of STAT proteins (signal transducer and activator of transcription) in the cytoplasm.
Human interferon gamma receptor 2 has been localized to chromosome arm 21q, a region which is known to confer resistance to the encephalomyocarditis virus (Cook et al., J Biol Chem, 1994, 269, 7013-7018).
Complete absence of human IFN-gamma responsiveness due to a mutation in either interferon gamma receptor 1 or interferon gamma receptor 2 is typically associated with severe mycobacterial infections in lungs, viscera, lymph nodes, blood and bone marrow (Dorman and Holland, Cytokine Growth Factor Rev., 2000, 11, 321-333). A clinical phenotype associated with autosomal dominant mutations of interferon gamma receptor 1 (leading to partial interferon gamma 1 deficiency is milder than seen in individuals with complete absence of IFN-gamma responsiveness and infections are usually responsive to appropriate antimicrobial therapy (Dorman and Holland, Cytokine Growth Factor Rev., 2000, 11, 321-333).
The expression of the human interferon gamma receptor complex is modulated by environmental signals in human malignant T cells and thymocytes (Novelli et al., J. Immunol., 1994, 152, 496-504). The upregulation of IFN-gamma expression promotes T cell proliferation in T cells with low levels of interferon gamma receptor complex and apoptosis in T cells with high levels of interferon gamma receptor complex (Novelli et al., J. Immunol., 1994, 152, 496-504).
Although IFN-gamma signaling typically exerts antiviral effects, in some cases of bacterial infections, endogenous IFN-gamma can act as a detriment to the host. In the case of HIV infection, activation of monocytoid cells by IFN-gamma signaling was found to stimulate rather than inhibit virus replication (Biswas et al., J. Exp. Med., 1992, 176, 739-750).
In addition, there are conflicting reports on the effects of IFN-gamma signaling on tumor growth in mice. For example, investigators have inserted the IFN-gamma gene into non-immunogenic murine tumor cells with high metastasizing potential and found that the IFN-gamma secreting cells had less ability to develop tumors than the parental cells (Gansbacher et al., Cancer Res., 1990, 50, 7820-7825). On the other hand, a metastasizing murine mammary carcinoma productively transfected with the IFN-gamma gene was found to metastasize more extensively than the untransfected tumor line (Ferrantini et al., J. Immunol., 1994, 153, 4604-4615).
In experimental animal models of autoimmune disease including: autoimmune thyroiditis, experimental autoimmune peripheral neuritis and autoimmune insulin-dependent diabetes, experimental autoimmune encephalomyelitis, autoimmune arthritis and autoimmune insulinitis, IFN-gamma was either found to facilitate induction of disease or to aggravate disease manifestations (Billiau, Adv. Immunol., 1996, 62, 61-130). Increased levels of IFN-gamma mRNA have been observed in intestinal propria lamina of Crohn's disease patients (Fais et al., J. Interferon Res., 1994, 14, 235-238).
Deregulation of IFN-gamma signaling has been implicated in autoimmune disease, complications due to viral infections and cancer. Furthermore, deregulated apoptosis signaling may impinge on other age-related disorders such as osteoporosis and atherosclerosis. Modulation of expression of components of the interferon gamma receptor complex, including interferon gamma receptor 2 may prove to be a useful strategy with which to down-regulate IFN-gamma signaling in cases where excessive signaling precipitates disease.
Attempts to modulate the process of IFN-gamma signaling have thus far been essentially limited to inhibition of IFN-gamma itself. Strategies aimed at inhibition of interferon gamma receptor 2 function are as yet untested as investigative or therapeutic protocols. Consequently there remains a long felt need for agents capable of effectively inhibiting interferon gamma receptor 2 function.
Antisense technology is emerging as an effective means for reducing the expression of specific gene products and may therefore prove to be uniquely useful in a number of therapeutic, diagnostic, and research applications for the modulation of interferon gamma receptor 2 expression.
The present invention provides compositions and methods for modulating interferon gamma receptor 2 expression.